An optical fiber ribbon is a collection of several small optical fibers side by side, all lying in a plane, enclosed in a matrix material made of a synthetic resin; the matrix material acts as a skin enclosing the optical fibers. This flat, side-by-side arrangement allows packing many optical fibers in a small cross-sectional area.
Sometimes one of the optical fibers in a ribbon needs to be repaired while the other fibers in the ribbon continue to carry light signals. To repair a damaged optical fiber without disturbing the live fibers, the resin skin must be removed from the optical fibers allowing access to the one or more fibers that must be repaired. Another, more frequent reason for accessing individual fibers in a ribbon is to splice one fiber to connect it to a piece of terminal equipment, leaving the other fibers intact until the ribbon is laid to another piece of terminal equipment. There is therefore a need to be able to remove the skin from an optical fiber ribbon along a length of the ribbon not necessarily starting at an end of the ribbon.
Several methods have been developed of making midpoint entry into an optical fiber ribbon to access the individual fibers encapsulated by the ribbon skin. These methods include cutting or scraping the skin off the fibers, and even only partially cutting (scoring) the skin and then mechanically removing it from the fibers. All of these methods, it is found, are likely to cause damage to the optical fibers, and so are undesirable.
Another method involves shearing the skin in some fashion, such as bending, tearing, pinching, or fatiguing it to peel it away from the optical fibers. These methods mechanically disturb the fibers of the ribbon well beyond the region where access is required; this rearranging the fibers decreases the packing density, compared to what is possible with the fibers arranged in the ribbon as originally manufactured.
Another method uses a solvent to dissolve or weaken the skin material so that it falls away or is easily peeled away from the optical fibers. This method, however, tends to remove the coating of the optical fibers which is often color coded, and, in addition, often requires a little more patience than a worker in the field is inclined to demonstrate.
A last method uses adhesive tape and, optionally, a strong liquid adhesive. Here the section of the optical fiber ribbon bearing the optical fibers to be accessed is pressed onto an adhesive tape and then pulled off the tape, leaving behind at least some of the skin from the span of ribbon to be stripped. Sometimes a strong liquid adhesive, such as cyanoacrylate, is used with the tape. The strong liquid adhesive is applied at the point on the ribbon where entry is desired. That point on the ribbon is then pressed onto a surface adjacent the adhesive tape. Finally, the optical fiber ribbon is pulled up and away, the strong liquid adhesive ensuring that the skin will tear and at least some will remain behind, adhered to the tape.
In this method, the prior art teaches using double-sided tape and a separate thin work panel on which the strong liquid adhesive is deposited and to which the ribbon at the desired point of entry is glued. This method suffers from at least two drawbacks. First, there must be in the immediate vicinity a substantially flat and clean surface onto which the double-sided adhesive tape can be adhered. Second, since the work panel on which the strong liquid adhesive is deposited will have some thickness, there will be a length of ribbon not adhered to the double-sided tape between where the ribbon is glued and where it first adheres to the tape. So when the ribbon is pulled away from where it is glued there will be a slight jerk, tending to remove the ribbon from the tape without further removing the skin from the fibers. In addition, after removing the ribbon skin from the fibers, the double-sided tape must be removed from the surface it was pressed onto. This residue of tape and skin can be difficult to remove from the surface bearing the tape, making cleanup challenging.
In accessing fibers in ribbon mid-span, it is very important to take precaution against bending the ribbon too much. If the fibers are live, then overbending the ribbon can cause attenuation of the light signal, disrupting or garbling communication. Even if the fibers are not live, it is important not to overbend the ribbon because the stress it causes could fracture the ribbon or fatigue the ribbon matrix so that it fractures later, and moreover, imparts to the optical fibers in the ribbon needless bending stresses.
The present invention provides a fast, simple method, not requiring great manual dexterity or skill, and so is unlikely to damage the fibers, and allows access to a well-defined span of the ribbon. In the present invention, the length of ribbon not adhered to a surface is insignificant, so there is little tendency for the slight jerk that occurs when pulling the ribbon in prior art methods. Just as importantly, the method of the present invention is environmentally friendly; it leaves no residue that is not easily picked up and carried off for appropriate disposal. In addition, the present invention includes a precaution against overbending the ribbon, ensuring the full life of the ribbon and guarding against disrupting communication when fibers are accessed in a ribbon with live fibers.